Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{instock:[{warehouse:"A",qty:5},{warehouse:"C"},{warehouse:"B",qty:6},]}]
Query
db.collection.aggregate([{$project:{instock1:{$filter:{input:"$instock",as:"cc",cond:{$eq:["$$cc.warehouse","A"]}}}}}])
Result